SUPPLEMENT to the Double Hule of Chree.

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QUESTIONS.

1. WHAT is the Double Rule of Three; or COMPOUND Proportion

2. How are questions to be stated in the Double Rule of Three?

3. How is it known, after the statement of the question, whether the propor,

tion be direct or inverse?

4. WHEN the proportion is Direct, how is the answer to be found? 5. WHEN the proportion is Inverse, how is the answer to be found?

EXERCISES,

1. Ix 6 men build a wall 20 feet long, 6 feet high, and 4 feet wide in 16 days, in what time will 24 men build one 200 feet long, 8 feet high and 6 feet thick?

Ansower 80.days THE solid contents

in each piece of wall, according to the giv, en dimensions, must be found before state ing the question.

2, IF the freight of 12 Cut. 2qrs. 6lb. 275 miles, cost Dolls. 27,78: how far may 60 Ct. 3qrs. be shipped for Dolls. 234,78 ?

Ans. 480 miles,

3. An usurer put out 75 dollars, at [ interest; and at the end of 8 months received for principal and interest, 79 dollars; I demand at what rate per | sent he received interest ?

Ans. 8 per cent.

4. Ir 7 men can make 84 rods of wall in 6 days; în what time will 10 men make 150 rods?

Ans. 71⁄2 days.

5. IF the freight of 9hhds. of sugar, each weighing 12 Cut. 20 leagues, cost 16: what must be paid for the freight of 50 tierces ditto, each weighing 2 Cat. 100 leagues? Ans. 92 11 10

"PRACTICE is a contraction of the Rule of Three direct, when the first term happens to be an unit, or one; it has its name from its daily use among Merchants and Tradesmen, being an easy and concise method of working most questions, which occur in trade and business."

PROOF. By the Single Rule of Three, Compound Multiplication, or by varying the Parts.

BEFORE any advances are made in this rule, the Learner must commit to memory, the following

In Pounds, Shill. Pence, Farthings. In Dollars, Cents, Mills.

WHEN the price of the given quantity is 1 18. or 1d. per pound, yard, &c. then will the quantity itself be the answer at the supposed price. Therefore,

CASE. 1.

WHEN the price of 1 yd. lb. &c. consists of farthings only; If it be one farthing, take a fourth of the quantity; if a half penny, take a half; if three farthings take a half and a fourth of the quantity and add them. This gives the value in pence, which must be reduced to pounds.

RULE.

MULTIPLY the quantity by the price of 1 pound, yard, &c. the product will be the answer.